Being physically active is one of the most important steps that
Americans of all ages can take to improve their health. This
inaugural Physical Activity Guidelines for Americans provides
science-based guidance to help Americans aged 6 and older improve their health
through appropriate physical activity.

The U.S. Department of Health and Human Services (HHS) issues the
Physical Activity Guidelines for Americans. The content of the
Physical Activity Guidelines complements the Dietary Guidelines
for Americans, a joint effort of HHS and the U.S. Department of
Agriculture (USDA). Together, the two documents provide guidance on the
importance of being physically active and eating a healthy diet to promote good
health and reduce the risk of chronic diseases.

This chapter provides background information about the rationale and
process for developing the Guidelines. It then discusses several issues that
provide the framework for understanding the Guidelines. The chapter also
explains how these Guidelines fit in with other published physical activity
recommendations and how they should be used in practice.

Why and How the Guidelines Were Developed

The Rationale for Physical Activity Guidelines

We clearly know enough now to recommend that all Americans should
engage in regular physical activity to improve overall health and to reduce
risk of many health problems. Physical activity is a leading example of how
lifestyle choices have a profound effect on health. The choices we make about
other lifestyle factors, such as diet, smoking, and alcohol use, also have
important and independent effects on our health.

The primary audiences for the Physical Activity Guidelines for
Americans are policymakers and health professionals. The Guidelines are
designed to provide information and guidance on the types and amounts of
physical activity that provide substantial health benefits. This information
may also be useful to interested members of the public. The main idea behind
the Guidelines is that regular physical activity over months and years can
produce long-term health benefits. Realizing these benefits requires physical
activity each week.

These Guidelines are necessary because of the importance of physical
activity to the health of Americans, whose current inactivity puts them at
unnecessary risk. Healthy People 2010 set objectives for increasing
the level of physical activity in Americans over the decade from 2000 to 2010.
Unfortunately, the latest information shows that inactivity among American
adults and youth remains relatively high and that little progress has been made
in meeting these objectives.

The Development of the Physical Activity Guidelines for Americans

Since 1995 the Dietary Guidelines for Americans has included
advice on physical activity. However, with the development of a firm science
base on the health benefits of physical activity, HHS began to consider whether
separate physical activity guidelines were appropriate. With the help of the
Institute of Medicine, HHS convened a workshop in October 2006 to address this
question. The workshop's report, Adequacy of Evidence for Physical
Activity Guidelines Development (http://www.nap.edu/catalog.php?record_id=11819
), affirmed that advances in the science of
physical activity and health justified the creation of separate physical
activity guidelines.

The steps used to develop the Physical Activity Guidelines for
Americans were similar to those used for the Dietary Guidelines for
Americans. In 2007 HHS Secretary Mike Leavitt appointed an external
scientific advisory committee called the Physical Activity Guidelines Advisory
Committee. The Advisory Committee conducted an extensive analysis of the
scientific information on physical activity and health. The Physical
Activity Guidelines Advisory Committee Report, 2008 and meeting summaries
are available at http://www.health.gov/paguidelines/guidelines/committee.aspx.

HHS primarily used the Advisory Committee's report but also
considered comments from the public and Government agencies when writing the
Guidelines. The Guidelines will be widely promoted through various
communications strategies, such as materials for the public, Web sites, and
partnerships with organizations that promote physical activity.

The Framework for the Physical Activity Guidelines for Americans

The Advisory Committee report provided the content and conceptual
underpinning for the Guidelines. The main elements of this framework are
described in the following sections.

Baseline Activity Versus Health-Enhancing Physical Activity

Physical activity has been defined as any bodily movement produced by
the contraction of skeletal muscle that increases energy expenditure above a
basal level. However, in this document, the term "physical activity"
will generally refer to bodily movement that enhances health. Bodily movement
can be divided into two categories:

Baseline activity refers to the light-intensity
activities of daily life, such as standing, walking slowly, and lifting
lightweight objects. People vary in how much baseline activity they do. People
who do only baseline activity are considered to be inactive. They may do very
short episodes of moderate- or vigorous-intensity activity, such as climbing a
few flights of stairs, but these episodes aren't long enough to count
toward meeting the Guidelines. The Guidelines don't comment on how
variations in types and amounts of baseline physical activity might affect
health, as this was not addressed by the Advisory Committee report.

Health-enhancing physical activity is activity that,
when added to baseline activity, produces health benefits. In this document,
the term "physical activity" generally refers to health-enhancing
physical activity. Brisk walking, jumping rope, dancing, lifting weights,
climbing on playground equipment at recess, and doing yoga are all examples of
physical activity. Some people (such as postal carriers or carpenters on
construction sites) may get enough physical activity on the job to meet the
Guidelines.

We don't understand enough about whether doing more baseline
activity results in health benefits. Even so, efforts to promote baseline
activities are justifiable.

In this document, the term "physical activity" will
generally refer to bodily movement that enhances health.

After all, baseline activities are normal lifestyle
activities. Encouraging Americans to increase their baseline activity
is sensible for several reasons:

Increasing baseline activity burns calories, which can help in
maintaining a healthy body weight.

Some baseline activities are weight-bearing and may improve bone
health.

There are reasons other than health to encourage more baseline
activity. For example, walking short distances instead of driving can help
reduce traffic congestion and the resulting air pollution.

Encouraging baseline activities helps build a culture where physical
activity in general is the social norm.

Short episodes of activity are appropriate for people who were
inactive and have started to gradually increase their level of activity, and
for older adults whose activity may be limited by chronic conditions.

The availability of infrastructure to support short episodes of
activity is therefore important. For example, people should have the option of
using sidewalks and paths to walk between buildings at a worksite, rather than
having to drive. People should also have the option of taking the stairs
instead of using an elevator.

Health Benefits Versus Other Reasons To Be Physically Active

Although the Guidelines focus on the health benefits of physical
activity, these benefits are not the only reason why people are active.
Physical activity gives people a chance to have fun, be with friends and
family, enjoy the outdoors, improve their personal appearance, and improve
their fitness so that they can participate in more intensive
physical activity or sporting events. Some people are active because they feel
it gives them certain health benefits (such as feeling more energetic) that
aren't yet conclusively proven for the general population.

The Guidelines encourage people to be physically active for any and all
reasons that are meaningful for them. Nothing in the Guidelines is intended to
mean that health benefits are the only reason to do physical activity.

Focus on Disease Prevention

The Guidelines focus on preventive effects of physical activity, which
include lowering the risk of developing chronic diseases such as heart disease
and type 2 diabetes.

Physical activity also has beneficial therapeutic effects and is
commonly recommended as part of the treatment for medical conditions. The
Advisory Committee report did not review the therapeutic effects of activity,
and the Guidelines do not discuss the use of physical activity as medical
treatment.

Health-Related Versus Performance-Related Fitness

The Guidelines focus on reducing the risk of chronic disease and
promoting health-related fitness, particularly cardiovascular
and muscular fitness. People can gain this kind of fitness by doing the amount
and types of activities recommended in the Guidelines.

The Guidelines do not address the types and amounts of activity
necessary to improve performance-related fitness.
Athletes need this kind of fitness when they compete. Medical screening issues
for competitive athletes also are outside the scope of the Guidelines.

People who are interested in training programs to increase
performance-related fitness should seek advice from other sources. Generally,
these people do much more activity than required to meet the Guidelines.

Lifespan Approach

The best way to be physically active is to be active for life.
Therefore, the Guidelines take a lifespan approach and provide recommendations
for three age groups: Children and Adolescents, Adults, and Older Adults.

The Physical Activity Guidelines are for Americans aged 6 and
older. The Advisory Committee report did not review evidence for children
younger than age 6. Physical activity in infants and young children is, of
course, necessary for healthy growth and development. Children younger than 6
should be physically active in ways appropriate for their age and stage of
development.

Individualized Health Goals

The Guidelines generally explain the amounts and types of physical
activity needed for health benefits. Within these overall parameters,
individuals have many choices about appropriate types and amounts of activity.

To make these choices, American adults need to set personal goals for
physical activity. Setting these goals involves questions like, "How
physically fit do I want to be?" "How important is it to me to reduce
my risk of heart disease and diabetes?" "How important is it to me to
reduce my risk of falls and hip fracture?" "How much weight do I want
to lose and keep off?"

People can meet the Guidelines and their own personal goals through
different amounts and types of activity. Written materials, health-care
providers, and fitness professionals can provide useful information and help
people set and carry out specific goals.

Four Levels of Physical Activity

The Advisory Committee report provides the basis for dividing the
amount of aerobic physical activity an adult gets every week
into four categories: inactive, low, medium, and high (see table below). This
classification is useful because these categories provide a rule of thumb of
how total amount of physical activity is related to health benefits. Low
amounts of activity provide some benefits; medium amounts provide substantial
benefits; and high amounts provide even greater benefits.

Classification of Total Weekly Amounts of Aerobic Physical Activity
Into Four Categories

Levels of Physical Activity

Range of Moderate-Intensity Minutes a
Week

Summary of Overall Health Benefits

Comment

Inactive

No activity beyond baseline

None

Being inactive is unhealthy.

Low

Activity beyond baseline but fewer than 150 minutes a
week

Some

Low levels of activity are clearly preferable to an inactive
lifestyle.

Medium

150 minutes to 300 minutes a week

Substantial

Activity at the high end of this range has additional and more
extensive health benefits than activity at the low end.

High

More than 300 minutes a week

Additional

Current science does not allow researchers to identify an upper
limit of activity above which there are no additional health benefits.

Action is needed at the individual, community, and societal levels to
help Americans become physically active.

Medium activity is 150 minutes to 300 (5 hours)
minutes of moderate-intensity activity a week (or 75 to 150 minutes of
vigorous-intensity physical activity a week). In scientific
terms, this range is approximately equivalent to 500 to 1,000 metabolic
equivalent (MET) minutes a week.

High activity is more than the equivalent of 300
minutes of moderate-intensity physical activity a week.

For More Information

Appendix 1 provides a detailed explanation of MET-minutes, a unit
useful for describing the energy expenditure of a specific physical
activity.

Relationship to Previous Public Health Recommendations

In 1995 the Centers for Disease Control and Prevention (CDC) and the
American College of Sports Medicine (ACSM) published physical activity
recommendations for public health. The report stated that adults should
accumulate at least 30 minutes a day of
moderate–intensity physical activity on most, preferably all, days per
week. In 1996 Physical Activity and Health: A Report of the
Surgeon General supported this same recommendation.

In order to track the percentage of adults who meet this guideline, CDC
specified that "most" days per week was 5 days. Since 1995 the common
recommendation has been that adults obtain at least 30 minutes of
moderate-intensity physical activity on 5 or more days a week, for a total of
at least 150 minutes a week.

The Physical Activity Guidelines for Americans affirms that it
is acceptable to follow the CDC/ACSM recommendation and similar
recommendations. However, according to the Advisory Committee report, the
CDC/ACSM guideline was too specific. In other words, existing scientific
evidence does not allow researchers to say, for example, whether the health
benefits of 30 minutes on 5 days a week are any different from the health
benefits of 50 minutes on 3 days a week. As a result, the new Guidelines allow
a person to accumulate 150 minutes a week in various ways.

Putting the Guidelines Into Practice

Although the Advisory Committee did not review strategies to promote
physical activity, action is needed at the individual, community, and societal
levels to help Americans become physically active. Publications such as the
Guide to Community Preventive
Services) (http://www.thecommunityguide.org/pa/)
and the recommendations of the U.S.
Preventive Services Task Force (http://www.uspreventiveservicestaskforce.org/Page/Name/recommendations)
summarize evidence-based strategies for promoting physical activity on the
community level and through primary health care. Accordingly, the final chapter
of the Physical Activity Guidelines for Americans provides only a
brief discussion on promoting physical activity, and indicates how to link the
Guidelines to action strategies.

Assessing Whether Physical Activity Programs Are Consistent With the
Guidelines

Programs that provide opportunities for physical activity, such as
classes or community activities, can help people meet the Guidelines. These
programs do not have to provide all, or even most, of the recommended weekly
activity. For example, a mall walking program for older adults may meet only
once a week yet provide useful amounts of activity, as long as people get the
rest of their weekly recommended activity on other days.

Programs that are consistent with the Guidelines:

Provide advice and education consistent with the Guidelines;

Add episodes of activity that count toward meeting the Guidelines;
and

May also include activities, such as stretching or warming up and
cooling down, whose health benefits are not yet proven but that are often used
in effective physical activity programs.

The Importance of Understandable Guidelines

HHS has tried to keep the Physical Activity Guidelines straightforward
and clear, while remaining consistent with complex scientific information. In
each chapter the key Guidelines are set apart from the text, in order to
identify the most important information to communicate to the public. The
messages contained in these Guidelines should be disseminated to the general
public and to anyone involved in promoting physical activity.